Method of manufacturing acoustic impedance elements



Feb. 9, 1932. I E 1,844,108

METHOD OF MANUFACTURING ACOUSTIC IMPEDANGEE-MILEMENTS Filed June 19,1930 S-Sheets-Sheet 1 INVENTOP E. H SMVTHE 7 BY ATTORNEY E. H. SMYTHEFeb. 9, 1932.

METHOD MANUFACTURING ACOUSTIC IMPEDANCE ELEMENTS Fil ed June 19. 1930 '3Sheets Sheet 2 FIG. I0

lNVE/VTOR 5. H. SMVTHE ATTORNEY Feb. 9, 1932. SMYTHE 4 1,844,108

METHOD OF MANUFACTURING ACOUSTIC IMPEDANCE ELEMENTS Filed June 19, 19393 Sheets-Sheet 3.

FIG. /4

FIG. /5

YINVENTOR E. H. SM) THE alwam A TTORNEV 10 way. The results desired tocircular in on," i s of I a composite layer. onaflatcoremaybeiledinstacksofdesireddimenterialnottobeattackedby Patented Feb. 9, 1932'UNITED STATES PATENT OFFICE- nnwm a. marina, or aversion, minors,sssienon mo m1. mnrnon nanomroams, moonrom'rnn, or new roan; n. Y, acbarona'rron or new you:

mnon or immacrnnme scenario nmmncn Application fled June 19, mo. sum Io.mus.

This invention relates to acoustic impedance elements of resistive orenergy dissipa- An object of this invention is to manufacturecacousticimpedance elements of predetermined characteristics in a variety ofconfigurations and sizes ina sim 1e and accurate s obtained with anacoustic impedance element being known, the dimensions-breadth, widthand length of the acoustic passage-ways therein-may be determined inaccordance with the disclosure 15 in the pending application of P. B.Flanders,

Serial No. 273,523, filed April 28, 1928.

In accordance with this invention and in its preferable form, layers oftwo materials, one ,of which is later to be dissolved out or othersowise removed, are alternately plated upon a conducting core until acompos te layer of the desired thickness is obtained, having a de-'sired number of layers of material, each layer of a desired thicknessand that of the mamin a be dissolved out, being such that when removedin a solvent, apertures of redetermined dimension are obtained.- en

. the composite layer is built up to the desired is or the dairedthicknessmay be cut therefrom, each slice provided withstrengthmeansupononeor each surface and then 'p in a solvent whereby the solubleis dissolved out,

degree, and-if the core 168V? a grid-work, the apertures in which provie sound ways of predetermined acoustic pro In another Olin .t

after having been built up cut imam}? dfirml together-by latlng' "sionanp a thinlayer ofmateriil th thesolventtobe usedtoremove one of thealternatelyplated or by slim facso erespecti' ve pstogether.maythenbe'cnt fromfisbarandsubjectetltotheactionofanhppropriatesolventtodissolveoutoneofthematerialsusedinforminglt of invention,

said mathe adjacent 's'urthe composite layer. When the thin plating isemployed to secure the strips into a single bar, no other su port isnecessary to maintain the non'dissolved material properlyspaced. When,however, the strips are' sweated together, a supporting frame-work ononeqreach In still another embodiment of tion, individual acoustic immaybe manufactured by usmg ductive material and mounting alternatelyinvennee elements thereon washer-like members of conductivematerial andof non-conductive material, the latter being, preferably, of largerdiameter than the former. The asembly is then immersed alternately inlating baths of chosen materials thereby b ding up on each individualcondudive washer, annuli'of the two 'material sh Upon completion ofthe'plating operations, subunit is removed from the core, provided with asupporting frame-work or the immersed in an appropriate solution w y oneof the plat materials. ma be dis olved out;

the embodiments of a core of 'conthe, invention :dehereinbefore, it hasbeen said-that" when a unit or slice of the desimdthickness is obtainedit should be provided with, strengthening meansor asuppo work-before oneof the alternately-plated materials is out or otherwise m.- moved.Instead of providing this onthe of said slioeor unit, radial bands ofmaterial of groater-width than the of the'slicc or unit may be paintedthereon? Then, whm, the slice or- A i-a as sectiontoutedunitissubjectedto the action-ofana v priate solutio theportionstheinsula g -ds will not' as attacked as. freeportions and-a umthavingthedesimdacoustic-p ysandintegralsup isobtamed. U

Amorecomletezund offliis inventiomwill :2, 211,, which follows held inspaced relation afterthe insulating The ma rials whic ers .0

Fig.1 except that the composite layer is 4 built up on a tubular member;

acoustic impedance elements may be obtained;

Fig. 3 illustrates one step in providing a slice cut from the bar ofFig. 2 with a supporting frame-work;

Fig. 3--A illustrates an alternative method to provide a slice cut fromthe bar of Fig. 2 with a supporting structure,

Fig. 4 shows the slice of Fig. 3 after being provided with a supportingframe-workand dipped in an appropriate solvent to dissolve. out thelayers of one material;

5 Bgig. 5 is a section of Fig. 4 along the line -Fig. 6 illustrates theapplication of an acoustic impedance element in an acoustic channel;

Fig. 7 illustrates a modification of the method comprising thisinvention;

Fig. 8 is a section of the showing in Fig. 7 along the line 8-8;

Figs. 9, 10 and 11 and 11A illustrate stages in carrying out anotherapplication of this invention employing the composite layer shown inFigs. 7 and 8;

Fig. 12 shows another embodiment of the composite layer of Figs. 7 and 8from which acoustic impedance elements may be formed;

Figs. 13 and 14 illustrate-the application of this invention to theformation of individual acoustic impedance elements;

Fig. 15 illustrates .a use in an acoustic channel of acoustic impedancesmanufactured in accordance with this invention.

There is shown in Fi s. 1 and 2 a cylindrical core member 1 of eectrically conductive material, not soluble in the solutions in which itis immersed, upon which has been built up a COIDFOSltB layer 2comprising alternate laymaterials 3 and 4 which have been plated thereonand upon one another by immersmg the conductive core as anelectrodefirst a plating bath of one material and then mto that of the other.Before alternate immersions the last layer of plating material 1s rinsedin an appropriate solutlon and may if desired be lished or buffed tosmooth out irregularities on its surface and to provide a good platinsurface for the succeedmg layer of materia As shown in Fig. 1A, atubular core member 5 may be employed in preference to the solid core 1.

1 From the composite bar shown in Fig. 2,

I a slice 13 of the desired thickness may be cutandon; one or eachsurface coated, as

in' Fig. 3, with an insulating paint'6 except on those portions .9whereon it is desired to plate a supporting and insoluble frameworkwhereby alternate annuli of the slice may be .to, for instance:

. however, a thic coating has been washed off and the slice 13 immersedin an appropriate solution whereby the alternate layers of the material4. are dissolved out, leaving the structure shown in Figs. 4and 5: anacoustic impedance element provided with a supporting rib structure 10,

and defining a plurality of concentric acoustic channels 11.

Fig. 3-A shows another method of providing the acoustic device with asupporting structure for its unit or slice. Each surface, preferably, ofthe slice 13 is coated with radial bands 46 of an insulating material,said bands being greater width than the thickness and concentric annuli3 in spaced relationv of the slice and not being subject to the actionof the solvent or other means used to remove one of the materials fromthe slice. When the unit is immersed in an appropriate soluneed of asupporting frame-work on one or each surface of the unit.

The use of the acoustic unitso fabricated "in a sound channel whosecross sectional area is desired to be kept constant is illustrated-inFigure 6 wherein the core portion of the unit "13 has been reamed andtapped whereby .molded portions 16 and 17 may be mounted onopposite-surfaces thereof. The unit 13 may be secured by bolts 19between the flanges 15 of the acoustic channel defining members 18.

It will beunderstood that instead of using a cylindrical core and thusforming cylindrical acous'tic members, a core of any desired eometricalconfiguration may be employed ependent, of course, u on the use to whichthe unit obtained there rom is to be put and the characteristic desired.Furthermore,

after the slices of desired thickness are cut/ from the bar, asupporting frame-work need not necessarily be plated thereon but apreviously formed skeleton may be attached thereby soldering, sweatingor the like.

- In carrying out this invention, the material to be dlssolved is platedto a thickness determined ,by the characteristics desired in theacoustic impedance units. This thickness is between one mil and fivemils, although it may be less or reater as desired. Usually, es ofone'mil is employed whereby, if the transverse breadth and the length ofthe acoustic channels are of appropriatedimensions, an impedance unithaving a substantially resistive characteristic, only, may be obtained.It is to be understood, how ever, that this invention is in no wayrestricted to the manufacture of acoustic units of that characteristiconly. b It lmay e a ernate y tion when the unit was dipped into theappropriate. solvent after being provided with a supporting member.

Fig. 15 is illustrative of an application of acoustic impedance elementsformed in the ways previously outlined. Elements 40 are positioned in anacoustic channel 37 and are supported at their peripheries b a ring member '39 in spaced relation to efine an annular volume 42 and a member44, defining, an acoustic channel 38, which extends through the centralportions of said acoustic elements and is provided with aplurality ofvents 41 leading into the annular volume 42. It will be apparent thatthe structure shown is capable of a' variety of uses, for instance,providing a leakage path or a combined series and leakage path for theacoustic disturb- It is to be understood thatthe above de- Iscriptionrelates to what are believed to be erred methods only ofcarrying out this.

pre invention and that the latters scope is not to be limited other thanby the appended claims.

What is claimed is:-

l. The method of manufacturin .an apertured structure which comprisesormin a composite body of alternate layers of di erent materials,securing said layers tolmeans composite body of alternate layers of forholding themin spaced relation, and'afterwards-removing one of saidmaterials.

2. The method of manufacturin an apertured structure which comprisesormin a ferent materials, forming on one or both surfaces a frame-workintegral therewith, andafterwards removin one of said materials.

3..The method 0 manufacturing an apertured structure which comprisesforming a composite body of alternate layers of different materials byalternate electrodepositions of said materials, securing said layers toa common support, and afterwards removing one of said materials.

4. The method of manufacturing an apertured structure which comprisesimmersing a member as an electrode alternately in plat-- ing ,baths ofdifferent materials, thereby forming a composite layer thereon, providmga supporting frame-work for said layer,

and afterwards removing one of said materials to form a structure havinga plurality of passageways.

5. The method of manufacturing an ap ertured structure which comprisesforming a composite body of alternate adherent layers of differentmaterials, securing said layers to means for holding them in spacedrelation, and afterwards removing one of saidmate rials.

6. The method of manufacture which comprises forming a finely laminatedbi-metallic plate having the laminations parallel to the surface of theplate by alternate electrodepositions of said metals on a centralportion of said plate, securing alternate lammations, at least, to acommon support, and

- afterwards removing one of the materials to form a finely slottedstructure.

7. The method of manufacturing an aooustic impedance element whichcomprises immersing a conductive member alternatelyin plating baths ofdifferent materials, whereby a composite layer of alternate layersthereof is formed thereon, providing a supporting structure for saidlayer, and after-' wards removing one of said materials to form aslotted structure acoustic channels. v

8. The method of manufacturing an acoustic impedance element whichcomprises providing a plurality of" building up a composite layer ofaplurality of alternate layers of different materials, cutting slicesfrom said layer transverse to the planes of said alternate layers,securing said layers tomeans for holding them in spaced relation, andafterwards removing one of said materials to form a slottecLstruct-ure.

9. The method of manufacturing an acoustic-impedance element whichcomprises immersing a member as an electrode alternately in platingbaths of different materials, whereby a composite layer is formedthereontconsisting of alternate layers of said mas:

. terials, cutting said composite layer transverse: to the planes of itsalternate layers,-

whereby a slice of a desired thickness is obtained, securing said layersto a common supmaterials to form a slotted structure.

10. Themethod of manufacturing.

!10 z-port, and afterwards removing one of said acoustic impedanceelement which comprises forming a iinely laminated bi-metalliccoattherefrom a u'nitof desired thickness, associating supportin meansfor the laminations into said unit, an removing one of the metals 7 toform .a finely slotted structure..

11. The method of -manufacturing an 7 acoustic impedance element whichcomprises .electrodepositing. u n a conductivecore thin alternate layers0 a plurality of materials to form a composite layer, cutting therefroma slice of desired thickness, a sup- W porting frame-work on one or.both 0 .its sur faces, and thereafter removing one of the I 7 materialsto leave. a slotted structure.

The method of manufacturing usf ingon a core member, thereafter slicingi acoustic impedahce element which comprises immersing an electrodemember alternately in plating baths of diiierentimaterials, therebyfprming a composite layer thereon, re-

movmg said composite layer from said electrode, cutting said layer intostrips, piling the said strips in stacks, securing them togl'ether,cutting said stacks into slices and 'pping said slices into anappropriate solution whereby one of saidplated materials is dissolvedout leaving a structure with a plurality of apertures therein.

In witness whereof, I hereunto subscribe my name this 14th day of June,1930.

EDWIN H. SMYTHE.

